The Doctor attempts to destroy the giant maggots and cure Cliff but the real threat is BOSS, who is poised to take over all the world's computers.
Quest roles:
Richard Franklin(Mike Yates), Nicholas Courtney(Brig. Lethbridge-Stewart), Terry Walsh(Doran (uncredited)), John Levene(Sergeant Benton), Jerome Willis(Stevens), Stewart Bevan(Clifford Jones), John Dearth(Lupton), Mitzi McKenzie(Nancy)